Up to 40% of mother-to-child transmission (MTCT) of HIV occurs during breastfeeding BF, and two-thirds of BF-associated MTCT occurs among infants after 6 mo of age. Early BF cessation is recommended by WHO as one way to minimize MTCT, but several studies in developing countries have observed high rates of associated gastroenteritis, growth faltering, and mortality. This is not surprising since the 6 to 24 month period of life is a time when growth faltering is prevalent even among BF children of HIV-negative mothers. During this period, mean weight-for-age-Z scores (WAZ) and length-for-age-Z-scores (LAZ) of children living in Africa and Asia plummet to -1.5 to -2.5, followed by little or no recovery thereafter. The resulting underweight and stunting malnutrition underlies 50% and 35%, respectively, of all under-5 mortality, and results in long-term deficits in cognitive development, reduced school performance, and lower adult economic productivity. The 6 to 24 mo period is characterized by the gradual addition or other foods and liquids and with high rates of diarrheal disease. Efforts to enhance growth by improving complementary feeding practices among 6 to 24 mo old children have generally met with modest success: most improve WAZ and LAZ by 0.1 - 0.5 Z scores at 18 - 24 mo. Another literature indicates that provision of water and especially sanitation services, reduces diarrhea and enhances child growth, producing increases in WAZ and LAZ by the same order of magnitude as complementary feeding interventions. Furthermore, the effects on growth are greater than and independent of the effects on diarrhea, suggesting these services reduce subclinical enteric disease, which suppresses growth and is much more prevalent than diarrhea. This study will test the effectiveness of an intervention delivered to 500 HIV-positive mothers and their children from mid-gestation to 24 mos. The intervention will include sanitation services (provision of a latrine), improved hygiene (promotion of hand washing), and improved nutrition (promotion of exclusive BF from birth to 6 mo for all infants;promotion of expressed and heat-treated breast milk (no direct BF) for HIV-exposed infants testing PCR-negative at 6 months and continued BF for exposed infants testing PCR-positive at 6 months;improved feeding practices;and provision of Nutributter, a micronutrient fortified food). All interventions will be delivered by an existing (albeit strengthened) village health worker network in the community. Primary infant outcomes will be: infection-free survival at 24 months among 6-mo PCR- negative infants;hemoglobin at 12 and 18 months;and linear and ponderal growth. PUBLIC HEALTH RELEVANCE: Each year, 200,000 infants are infected with HIV during breastfeeding, so the World Health Organization recommends that HIV-positive mothers stop breastfeeding to reduce this transmission. Unfortunately, not breastfeeding in resource-constrained settings is associated with high rates of diarrhea, poor growth, and death. This study will test provision of a nutrition, sanitation, and hygiene intervention as an approach to minimize HIV-exposure while also promoting growth and health in young children born to HIV-positive mothers in developing countries.